Interspecific hybridization is a route for transgenes from genetically modified (GM) animals to invade wild populations, yet the ecological effects and potential risks that may emerge from such hybridization are unknown. Through experimental crosses, we demonstrate transmission of a growth hormone transgene via hybridization between a candidate for commercial aquaculture production, GM Atlantic salmon (Salmo salar) and closely related wild brown trout (Salmo trutta). Transgenic hybrids were viable and grew more rapidly than transgenic salmon and other non-transgenic crosses in hatchery-like conditions. In stream mesocosms designed to more closely emulate natural conditions, transgenic hybrids appeared to express competitive dominance and suppressed the growth of transgenic and non-transgenic (wild-type) salmon by 82 and 54 per cent, respectively. To the best of our knowledge, this is the first demonstration of environmental impacts of hybridization between a GM animal and a closely related species. These results provide empirical evidence of the first steps towards introgression of foreign transgenes into the genomes of new species and contribute to the growing evidence that transgenic animals have complex and context-specific interactions with wild populations. We suggest that interspecific hybridization be explicitly considered when assessing the environmental consequences should transgenic animals escape to nature.

We shouldn’t be too down hearted. GM salmon are not in commercial use, nor is it likely in the foresable future. Especially in Europe the use of GM salmon on farms would be commercially suicidal, the European consumer rightly has a deep mistrust of GM animal production. Though in my view work should continue on GM fishfeed development as this doesn’t alter the fish per se and will alleviate the pressure on finite resources of fishmeal and fishoil allowing more vegetable substitution in salmon diets.

you could GM plant oil e.g. rape-seed oil to contain more long chain omega 3 fatty acids for example. this would actually improve the flesh of the fish that it was fed to, and reduce the need to feed it on fish oils derived from wild caught fish.

i hasten to add that GM feed is not currently used in salmon aquaculture, but i’m simply making the point that GM could be part of the solution for saving finite stocks of fish being used for fishmeal and fishoil.